Artificial illumination on a Kuiper Belt Object would stand out because it would vary less than reflected sunlight does when the world moved toward or away from the sun.

"Just by checking for how their brightness varies with distance, you would be able to identify interesting candidates."

Princeton's Edwin Turner, a co-author of the new study. Unfortunately, Turner says, no telescopes currently in the works would be powerful enough to identify city lights in other planetary systems. Unless the aliens like things really bright.

"Forthcoming facilities might be able to see artificial lighting on another world if it’s really much brighter than we use. It begins to become plausible that we could detect it. A million times would be for sure, and 10,000 times we might have a chance."